1. Field of the Invention
The present invention relates generally to semiconductor packages, and more particularly to a semiconductor package including internal conductive posts for electrical interface to interior bond pads of a semiconductor die.
2. Description of the Related Art
Semiconductor dies are conventionally enclosed in plastic packages that provide protection from hostile environments and enable electrical interconnection between the semiconductor die and an underlying substrate such as a printed circuit board (PCB) or motherboard. The elements of such a package include a metal leadframe, an integrated circuit or semiconductor die, bonding material to attach the semiconductor die to the leadframe, bond wires which electrically connect pads on the semiconductor die to individual leads of the leadframe, and a hard plastic encapsulant material which covers the other components and forms the exterior of the semiconductor package commonly referred to as the package body.
The leadframe is the central supporting structure of such a package, and is typically fabricated by chemically etching or mechanically stamping a metal strip. A portion of the leadframe is internal to the package, i.e., completely surrounded by the plastic encapsulant or package body. Portions of the leads of the leadframe extend externally from the package body or are partially exposed therein for use in electrically connecting the package to another component.
In the electronics industry, hand held portable applications such as cell phones, PDA's (Personal Digital Assistants), Bluetooth, and IMT2000 require semiconductor packages which are progressively smaller and lighter, yet of increasing performance. In many of the above-described conventional semiconductor packages wherein portions of the leads are partially exposed within the package body, such leads are typically included along only the peripheral edge of the package body. To meet the requirements of current hand held portable applications, the semiconductor packages used therein must have higher electrical performance and functionality, and thus increased numbers of leads which are electrically connectable to an external device. Although it has been suggested in the prior art to narrow the pitch of the leads formed at the periphery of the bottom surface of the package body to increase the number of leads, there are physical limitations in narrowing the lead pitch during the manufacture of the leadframe. Also, excessive narrowing in the lead pitch gives rise to a susceptibility of solder shorting between the leads when the semiconductor package is connected to an external device through the use of solder.
The need for increased numbers of leads is driven, in large measure, by semiconductor dies of increased functionality which include bond pads at both the central region and the periphery of a common surface thereof. In current semiconductor package designs, it is extremely difficult to connect both these peripheral and central bond pads to each of the leads, due to the necessity of extending certain ones of the leads to the center of the semiconductor die to interface to the central bond pads, while avoiding any contact between these extended leads and the peripheral bond pads of the semiconductor die. The present invention addresses these problems by providing a semiconductor package which, in addition to including leads which are electrically interfaced to peripheral bond pads of a semiconductor die, further includes one or more conductive posts which are an electrically interfaced to the central bond pads of the semiconductor die. These and other features of the present invention will be discussed in more detail below.